1. Field of the Invention
The present invention relates to a method of treating neurological conditions in a mammal by administering a hematopoietic growth factor such as granulocyte-colony stimulating factor (GCSF), granulocyte-macrophage colony stimulating factor (GMCSF), and/or other hematopoetic factors, for example, MCSF except for erythropoietin (EPO). The invention also provides methods of screening for compounds that bind to a GCSF or GMCSF receptor found on the surface of a neuronal cell; and which provides a neuroprotective, neuroproliferative and/or a STAT gene activation activity.
2. Discussion of the Related Art
Growth factors are proteins that are essentially involved in regulating survival, proliferation, maturation, and outgrowth of developing neuronal cells. For example, the expression of a large number of growth factors increases in response to various brain insults. Many factors display endogenous neuroprotective and neurotrophic effects (see Arvidsson A et al., Neuroscience 2001; 106:27-41; Larsson E, et al., J Cereb Blood Flow Metab 1999; 19:1220-8; Mattson M P, et al., J Neurotrauma 1994; 11:3-33; Semkova I, et al., Brain Res Brain Res Rev 1999; 30:176-88). These effects were also reported after exogenous administration in vitro and in vivo after brain trauma and stroke (see Semkova I., et al., Brain Res. Rev. 1999; 30:176-88; Fisher M, et al., J Cereb. Blood Flow Metab. 1995; 15:953-9; Schäbitz W R et al., Stroke 2001; 32:1226-33; Schäbitz W R, et al., Stroke 2000; 31:2212-7). After binding to high-affinity membrane receptors the effects of growth factors are mediated by a cascade of intracellular signal-transduction events (Kemie S G. et al., Arch Neurol 2000; 57:654-7), which induces cells to grow and differentiate; or provides trophic support for cell survival.
Granulocyte-colony stimulating factor (GCSF), a 20 kDa protein, together with tumor necrosis factor-α (TNF-α) and the interleukins is a member of the cytokine family of growth factors. GCSF is the major growth factor involved in the production of neutrophilic granulocytes.
GCSF exerts its function via the activation of a membrane receptor (GCSF receptor) that belongs to the super-family of hematopoietin receptors, also being referred to as class I cytokine receptors (de Koning and Touw, Curr. Opin. Hematol., 1996, 3, 180-4).
A number of receptors for lymphokines, hematopoietic growth factors, and growth hormone-related molecules have been found to share a common binding domain. These receptors are referred to as hematopoietin receptors and the corresponding ligands as hematopoietins. Further, hematopoietins have been subdivided into two major structural groups: Large/long and small/short hematopoietins. One subset of individual receptor chains that are part of receptor complexes for large hematopoietins contain common structural elements in their extracellular parts: an immunoglobin-like domain, a hematopoietin-receptor domain, and 3 fibronectin type-III domains (2 in the leptin receptor). This subgroup was designated the “gp130 family of receptors” (Mosley, et al., J. Biol. Chem. 1996, 271, 32635-43) and include Leptin receptor (LPTR), Granulocyte colony stimulating factor receptor (GCSFR), Interleukin-6/-11/LIF/OSM/CNTF common beta chain (GP130), Leukemia inhibiting factor receptor (LIFR), Oncostatin-M receptor beta chain (OSMR), Interleukin-12 receptor beta-1 chain (IL12RB1), Interleukin-12 receptor beta-2 chain (IL12RB2). These receptor chains homodimerize (GCSFR, GP130, LPTR) or heterodimerize (GP130 with LIFR or OSMR, IL12RB1 with IL12RB2) upon binding the cognate cytokine. In addition, a prosite consensus pattern is characteristic of this receptor family, which is:
N-x(4-S-x(28,35)-[LVIM]-x-W-x(0,3)—P-x(5,9)-[YF]-x(1,2)-[VILM]-x-W (SEQ ID NO:1)
GCSF stimulates proliferation, survival, and maturation of cells committed to the neutrophilic granulocyte lineage through binding to the specific GCSF receptor (GCSFR) (see Hartung T., et al., Curr. Opin. Hematol. 1998; 5:221-5). GCSFR mediated signaling activates the family of Signal Transducer and Activator of Transcription (STAT) proteins which translocate to the nucleus and regulate transcription (Darnell J E Jr., Science 1997; 277:1630-5). GCSF is typically used for the treatment of different kinds of neutropenia in humans. It is one of the few growth factors approved for clinical use. In particular, it is used to reduce chemotherapy (CT)-induced cytopenia (Viens et al., J. of Clin. Oncology, Vol. 20, No. 1, 2002:24-36). GCSF has also been implicated for therapeutic use in infectious diseases as potential adjunctive agent (Hübel et al., J. of Infectious Diseases, Vol. 185:1490-501, 2002). GCSF has reportedly been crystallized to some extent (EP 344 796), and the overall structure of GCSF has been surmised, but only on a gross level (Bazan, Immunology Today 11: 350-354 (1990); Parr et al. J. Molecular Recognition 8: 107-110 (1988)).
In recent years a number of growth factors such as bFGF and pharmaceutically promising substances such as thrombocyte adhesion blockers like anti-GP IIb/IIa and Abcizimab have been tested for neuroprotective efficacy in clinical studies. Unfortunately, none of these prevailed in the clinical studies. In particular, NMDA antagonists, free radical scavengers and glutamate antagonists failed or demonstrated severe side-effects. The list of substances such as anti-ICAM or inhibitors of the glutamate-mediated NO-synthetase that have tested positive in cell-based assays and animal models but failed in clinical studies is getting increasingly longer (De Keyser, et al. (1999), Trends Neurosci, 22, 535-40).
Most studies on cerebral ischemia and testing of pharmacological substances in vivo have only been concerned with the immediate effects of the drug or paradigm under investigation (i.e. infarct size 24 h after induction of the stroke). However, a more valid parameter of true efficacy of a particular substance is the long-term effect on functional recovery, which is also reflected in human stroke studies, where clinical scales (e.g., Scandinavian stroke scale, NIH scale, Barthel index) also reflect the ability to perform daily life activities. Recovery in the first few days after focal lesions may be due to resolution of edema or reperfusion of the ischemic penumbra. Much of the functional recovery after the acute phase is likely due to brain plasticity, with adjacent cortical areas of the brain taking over functions previously performed by the damaged regions (Chen R, Cohen L G, Hallett M. Neuroscience 2002; 111(4):761-73). The two main mechanisms proposed to explain reorganization are unmasking of previously present but functionally inactive connections and growth of new connections such as collateral sprouting (Chen R, Cohen L G, Hallett M. 2002 Neuroscience 2002; 111(4):761-73). Short term plastic changes are mediated by removing inhibition to excitatory synapses, which is likely due to reduced GABAergic inhibition (Kaas J H. Annu Rev Neurosci. 1991; 14:137-67; Jones E G. Cereb Cortex. 1993 September-October; 3(5):361-72.). Plasticity changes that occur over a longer time involve mechanisms in addition to the unmasking of latent synapses such as long-term potentiation (LTP), which requires NMDA receptor activation and increased intracellular calcium concentration (Hess and Donoghue, J Neurophysiol. 1994 71(6):2543-7). Long term changes also involve axonal regeneration and sprouting with alterations in synapse shape, number, size and type (Kaas J H. Annu Rev Neurosci. 1991; 14:137-67, 3:).
Stroke is the third-leading cause of death, and the main cause of disability in the western world. It presents a large socioeconomic burden. The etiology can be either ischemic (in the majority of cases) or hemorraghic. The cause of ischemic stroke is often embolic, or thrombotic. So far, there is no effective treatment for the majority of stroke patients. The only clinically proven drugs so far are tissue plasminogen activator (TPA) and Aspirin. After massive cell death in the immediate infarct core due to lack of glucose and oxygen, the infarct area expands for days, owing to secondary mechanisms such as glutamate excitotoxicity, apoptotic mechanisms, and generation of free radicals.
Amyotrophic lateral sclerosis (ALS; Lou-Gehrig's disease; Charcot's disease) is a neurodegenerative disorder with an annual incidence of 0.4 to 1.76 per 100.000 population (Adams et al., Principles of Neurology, 6th ed., New York, pp 1090-1095). It is the most common form of motor neuron disease with typical manifestations of generalized fasciculations, progressive atrophy and weakness of the skeletal muscles, spasticity and pyramidal tract signs, dysarthria, dysphagia, and dyspnea. The pathology consists principally in loss of nerve cells in the anterior horn of the spinal cord and motor nuclei of the lower brainstem, but can also include the first order motor neurons in the cortex. Pathogenesis of this devastating disease is still largely unknown, although the role of superoxide-dismutase (SOD 1) mutants in familial cases has been worked out quite well, which invokes an oxidative stress hypothesis. So far, more than 90 mutations in the SOD1 protein have been described, that can cause ALS (Cleveland and Rothstein (2001), Nat Rev Neurosci, 2, 806-19). Also, a role for neurofilaments in this disease was shown. Excitotoxicity, a mechanism evoked by an excess glutamate stimulation is also an important factor, exemplified by the beneficial role of Riluzole in human patients. Most convincingly shown in the SOD1 mutants, activation of caspases and apoptosis seems to be the common final pathway in ALS (Ishigaki, et al. (2002), J Neurochem, 82, 576-84, Li, et al. (2000), Science, 288, 335-9). Therefore, it seems that ALS also falls into the same general pathogenetic pattern that is also operative in other neurodegenerative diseases and stroke, e.g. glutamate involvement, oxidative stress, and programmed cell death.
Parkinson's disease is the most frequent movement disorder, with approximately 1 million patients in North America; about 1 percent of the population over the age of 65 years is affected. The core symptoms of the disease are rigor, tremor and akinesia (Adams et al., Principles of Neurology, 6th ed., New York, pp 1090-1095). The etiology of Parkinson's disease is not known. Nevertheless, a significant body of biochemical data from human brain autopsy studies and from animal models points to an ongoing process of oxidative stress in the substantia nigra, which could initiate dopaminergic neurodegeneration. Oxidative stress, as induced by the neurotoxins 6-hydroxydopamine and MPTP (N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine), has been used in animal models to investigate the process of neurodegeneration. Although a symptomatic therapy exists (e.g. L-DOPA plus a decarboxylase inhibitor; bromocriptine, pergolide as dopamin agonists; and anticholinergic agents such as trihexyphenidyl (artane)), there is a clear need for a causative therapy, e.g. a neuroprotective therapy, that really halts the disease progress. These animal models have been used to test the efficacy of radical scavengers, iron chelators, dopamine agonists, nitric oxide synthase inhibitors and certain calcium channel antagonists. Apoptotic mechanisms are clearly operative in the animal models as well as in the patient (Mochizuki, et al. (2001), Proc. Natl. Acad. Sci. USA, 98, 10918-23, Xu et al. (2002), Nat. Med., 8, 600-6, Viswanath, et al. (2001), J. Neurosci., 21, 9519-28, Hartmann, et al. (2002), Neurology, 58, 308-10). This pathophysiology with involvement of oxidative stress and apoptosis also places Parkinson's disease amongst the other neurodegenerative disorders and stroke.
Cerebral ischemia may result from a variety of causes that impair cerebral blood flow (CBF) and lead to deprivation of both oxygen and glucose. Traumatic brain injury (TBI), on the other hand, involves a primary mechanical impact that usually causes skull fracture and abruptly disrupts the brain parenchyma with shearing and tearing of blood vessels and brain tissue. This, in turn, triggers a cascade of events characterized by activation of molecular and cellular responses that lead to secondary injury. The evolution of such secondary damage is an active process in which many biochemical pathways are involved (Leker and Shohami (2002), Brain Res. Rev., 39, 55-73). Many similarities between the harmful pathways that lead to secondary cellular death in the penumbral ischemic zone and in the area exposed to secondary post-traumatic injury have been identified (e.g. excitotoxity by excess glutamate release, nitric oxide, reactive oxygen species, inflammation, and apoptosis (Leker and Shohami (2002), Brain Res. Rev., 39, 55-73)). In addition, early ischemic episodes are reported to occur after traumatic brain injury, adding a component of ischemia to the primary mechanical damage.
Cardiovascular disease is the major cause of death in western industrialized nations. In the United States, there are approximately 1 million deaths each year with nearly 50% of them being sudden and occurring outside the hospital (Zheng, et al. (2001), Circulation, 104, 2158-63). Cardio-pulmonary resuscitation (CPR) is attempted in 40-90 of 100,000 inhabitants annually, and restoration of spontaneous circulation (ROSC) is achieved in 25-50% of these patients. However, the hospital discharge rate following successful ROSC is only 2-10% (Bottiger, et al. (1999), Heart, 82, 674-9). Therefore, the vast majority of the cardiac arrest victims annually in the United States is not treated successfully. The major reason for the low survival rates after successful CPR, i.e., for postarrest in-hospital mortality, is persistent brain damage. Brain damage following cardiocirculatory arrest is related both to the short period of tolerance to hypoxic stress and to specific reperfusion disorders (Safar (1986), Circulation, 74, IV138-53, Hossmann (1993), Resuscitation, 26, 225-35). Initially, a higher number of patients can be stabilized hemodynamically after cardiocirculatory arrest; many of them, however, die due to central nervous system injury. The personal, social, and economic consequences of brain damage following cardiac arrest are devastating. One of the most important issues in cardiac arrest and resuscitation (“whole body ischemia and reperfusion”) research, therefore, is cerebral resuscitation and postarrest cerebral damage (Safar (1986), Circulation, 74, IV138-53, Safar, et al. (2002), Crit Care Med, 30, p. 140-4). Presently, it is not possible to decrease the primary damage to neurons that is caused by hypoxia during cardiac arrest by any post-arrest therapeutic measures. Major pathophysiological issues include hypoxia and subsequent necrosis, reperfusion injury with free radical formation and cellular calcium influx, release of excitatory amino acids, cerebral microcirculatory reperfusion disorders, and programmed neuronal death or apoptosis (Safar (1986), Circulation, 74, IV138-53, Safar et al. (2002), Crit Care Med, 30, 140-4).
Several clinical trials have attempted to improve neurological outcome after cardiac arrest without success. The therapeutic use of barbiturates (to enhance neuroprotection) or the use of calcium channel blockers (to reduce ischemia reperfusion damage) was tested (Group (1986), Am. J. Emerg. Med., 4, 72-86, Group (1986), N. Engl. J. Med., 314, 397-403, Group (1991), Control Clin. Trials, 12, 525-45, Group (1991), N. Engl. J. Med., 324, 1225-31). To date no specific post-arrest treatment options are available to improve neurological outcome following cardiocirculatory arrest in the clinical setting (with the possible exception of mild hypothermia and thrombolysis where the results of large, randomized, and controlled clinical trials are eagerly awaited (Safar et al (2002), Crit. Care Med., 30, 140-4)). Therefore, an innovative therapy to improve neurological outcome after cardiac arrest is crucial.
Multiple sclerosis is the prototype inflammatory autoimmune disorder of the central nervous system and, with a lifetime risk of one in 400, potentially the most common cause of neurological disability in young adults. Worldwide, there are about 2-5 million patients suffering from this disease (Compston and Coles (2002), Lancet, 359, 1221-31.). As with all complex traits, the disorder results from interplay between as yet unidentified environmental factors and susceptibility genes. Together, these factors trigger a cascade of events, involving engagement of the immune system, acute inflammatory injury of axons and glia, recovery of function and structural repair, post-inflammatory gliosis, and neurodegeneration. The sequential involvement of these processes underlies the clinical course characterized by episodes with recovery, episodes leaving persistent deficits, and secondary progression. The aim of treatment is to reduce the frequency, and limit the lasting effects of relapses, relieve symptoms, prevent disability arising from disease progression, and promote tissue repair.
Schizophrenia is one of the most common mental illnesses. About 1 of every 100 people (1% of the population) is affected by schizophrenia. This disorder is found throughout the world and in all races and cultures. Schizophrenia affects men and women in equal numbers, although on average, men appear to develop schizophrenia earlier than women. Generally, men show the first signs of schizophrenia in their mid 20s and women show the first signs in their late 20s. Schizophrenia has a tremendous cost to society, estimated at $32.5 billion per year in the US. Schizophrenia is characterized by several of the following symptoms: delusions, hallucinations, disorganized thinking and speech, negative symptoms (social withdrawal, absence of emotion and expression, reduced energy, motivation and activity), catatonia. The main therapy for schizophrenia is based on neuropleptics, such as chlorpromazine, haloperidol, olanzapine, clozapine, thioridazine, and others. However, neuroleptic treatment often does not reduce all of the symptoms of schizophrenia. Moreover, antipsychotic treatment can have severe side effects, such as tardive dyskinesias. The etiology of schizophrenia is not clear, although there seems to be a strong genetic influence. Recently, it has become clear that schizophrenia has at least some aspects of a neurodegenerative disease. In particular, MR studies have revealed rapid cortical grey matter loss in schizophrenic patients (Thompson, et al. (2001), Proc Natl Acad Sci US A, 98, 11650-5; Cannon, et al. (2002), Proc Natl Acad Sci USA, 99, 3228-33). Therefore, treatment of schizophrenics with neuroprotective medication such as GCSF or GMCSF or other hematopoetic factors is warranted.
In view of the above, there is a need for treating neurological and/or psychiatric conditions, such as neurological diseases that relate to the enhancement of plasticity and functional recovery, or cell-death in the nervous system. In particular, there is a need for treating neurological diseases by providing neuroprotection to the neural cells involved.